A global review of sediment source fingerprinting research incorporating fallout radiocesium (137Cs)

Abstract

Information on the main sources supplying deleterious sediment loads to river systems is needed to improve our understanding of soil erosion processes. In particular, it is important to quantify the respective contributions of surface and subsurface sources to material degrading waterbodies. Radiocesium (137 Cs), emitted during thermonuclear bomb testing (~1950-1980) and nuclear accidents provides significant discrimination between surface material exposed to atmospheric fallout and subsurface material sheltered from it. A systematic worldwide review of research articles (n=123) that used 137 Cs to trace sediment sources showed that the United Kingdom (n=24), Australia (n=23) and the United States (n=20) had the highest number of publications utilizing 137 Cs in a sediment tracing framework. In contrast, few studies were published for catchments in Africa (n=9) or South America (n=2). In the northern hemisphere, positive relationships were evident between 137 Cs activities in surface and subsurface sources and the proportion of thermonuclear bomb fallout. However, given the low proportions of fallout received in regions between 0-20°N and 0-20°S, the potential application of 137 Cs tracing techniques may be limited in this area of the world as well as in agricultural regions with severe soil erosion (i.e. Chinese Loess Plateau and South Africa). In total, 94% of the studies researching surface and subsurface sources that analyzed 137 Cs as a potential tracing property included this parameter in end-member mixing models. The main challenges for the future of this technique are mainly related to the access to ultra-low background gamma spectrometry facilities and the development of surrogate tracers. Future research should ensure that basic catchment information and details on the sampling design are properly documented to ensure studies are reproducible. Moreover, researchers should provide raw measurement data to help improve our global understanding of 137 Cs dynamics in soil erosion research.

Understanding the role of water and tillage erosion from <sup>239+240</sup>Pu tracer measurements using inverse modelling

“…The use of fallout radionuclides to determine soil redistribution patterns and rates over the past decades has been used in many studies in various study areas around the world (see reviews: Mabit et al, 2014;Alewell et al, 2017;Evrard et al, 2020) and contributed substantially to understanding soil degradation processes. However, the most frequently used fallout radionuclide, 137 Cs, faces upcoming limitations (Chernobyl fallout that adds to the global fallout over large parts of Europe and ongoing decay below the detection limit of standard measuring devices; also see Sect.…”

“…However, the most frequently used fallout radionuclide, 137 Cs, faces upcoming limitations (Chernobyl fallout that adds to the global fallout over large parts of Europe and ongoing decay below the detection limit of standard measuring devices; also see Sect. 1) in the use as a soil redistribution tracer (Evrard et al, 2020). The fallout radionuclide 239+240 Pu has demonstrated its suitability for determining the recent soil redistribution history (since the 1960s; see review in Alewell et al, 2017) and is a potential alternative for 137 Cs as a soil redistribution tracer (Mabit et al, 2013;Alewell et al, 2017).…”

“…The force of atmospheric nuclear weapon tests transported radioisotopes outside the troposphere, where circulation led to a (regionally) homogeneous spatial distribution and subsequent fallout on soils via precipitation (Meusburger et al, 2016). The main period of atmospheric nuclear weapon tests was from 1953 to 1964 (Schimmack et al, 2001), while the Test Ban Treaty caused a rapid decrease in atmospheric bomb tests in [1963][1964] (Wallbrink and Murray, 1993;Evrard et al, 2020). This rapid decrease led to a distinct peak in the activity of radioisotopes in soils, which enables the use of radioisotopes as redistribution tracers in soils (Alewell et al, 2017).…”

“…The radioisotope 137 Cs has been used as a soil redistribution tracer in a large number of studies (e.g. Porto and Walling, 2012;Chartin et al, 2013;Evrard et al, 2020) and has become a widely used method in soil ero-sion science. However, the Chernobyl disaster in 1986 supplied additional radioactive fallout to soils across large areas of Europe (Evangeliou et al, 2016).…”

Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)

“…These techniques are based on the analysis of multiple conservative properties both in the sediments and their potential sources. Fallout radionuclides (Wallbrink, 2004;Evrard et al, 2015;Wallbrink et al, 1998;Evrard et al, 2020), geochemical (Collins et al, 1997;Laceby and Olley, 2015) and mineral properties (Klages and Hsieh, 1975;Walden et al, 1997) are the most frequently used tracers to quantify sediment source contributions. The use of fallout radionuclides and https://doi.org/10.5194/soil-2020-48 Preprint.…”